A reducer valve is disclosed in U.S. Pat. No. 3,522,818 and adjusts an approximately constant back pressure independently of the pressure present in the pressurized-gas source. A piston having a valve body configured with a cylindrical shape is displaceably mounted in a valve housing against the force of a compression spring. The forward end of the valve body is provided with a seal disc with which a valve seat within the valve housing can be closed. The pressurized gas, which is at high pressure, flows via the valve seat into the valve housing and is correspondingly throttled depending upon the position of the valve body relative to the valve seat and reaches, via an outflow opening, a consumer connected downstream. The consumer can, for example, be in the form of an automatic lung which emits respirating gas to a carrier of an apparatus as required.
At one end, the piston is subjected to the pressure which is present at the outflow end of the valve body whereby the piston and the valve body are moved in a direction toward the valve seat. For this purpose, a closed volume is formed as a control pressure volume between one end of the piston and the inner surface of the valve housing. The control pressure space is connected to the pressure space downstream of the valve body. In this way, the control pressure space is charged with the back pressure present in the region of the outflow opening. The other end of the piston is at ambient pressure level. With increasing back pressure, the pressure in the control pressure space likewise increases so that a larger force acts on the piston and the valve body and the gas, which flows in via the valve seat, is correspondingly throttled until the back pressure again decreases.
It is disadvantageous in the known reducer valve that the valve body is moved away from the valve seat by the pressure spring for the case that the pressure in the pressurized gas source has dropped below the back pressure and the total residual gas can flow out of the pressurized gas source. Pressurized gases often still contain a certain residual moisture. For this reason, a condensation of water vapor can occur within the pressurized gas source whereby corrosion within the pressurized gas source is facilitated.